Evaluation of Heat Recovery Heat Exchanger Design Parameters for Heat-to-Power Conversion from Metallurgical Off-Gas

Abstract

Heat recovery heat exchangers for heat-to-power conversion from metallurgical off-gas should have a compact design that reduces component cost and footprint. The goal of our study is to investigate and identify key heat exchanger design parameters for minimizing the surface area of heat recovery heat exchangers. We explore the effect of basic heat exchanger design parameters on component and system performance through a combined Rankine cycle and heat exchanger optimization. We consider both "ideal" and "real" heat exchangers. The ideal heat exchangers are characterized by a minimum number of practical design constraints and provide a reference for the lowest achievable heat transfer surface area. The "real" heat exchangers are not based on detailed heat exchanger designs per se, but represent different practical design constraints inspired by well-known heat exchanger concepts. This approach enables evaluation of different heat exchanger types on a system level without detailed modelling of the heat exchangers. Results show that the different heat exchanger types result in significantly different surface areas under the investigated conditions. As expected, concepts that allow large differences between hot and cold side cross-sectional flow areas and hydraulic diameters can be better optimized to off-gas heat-to-power conversion. Thus, heat exchangers with these flexibilities, such as plate-and-fin type concepts, appear to be promising for off-gas heat-to-power conversion.